In the field of non-impact printing, the most common types of printers have been the thermal printer and the ink jet printer. When the performance of a non-impact printer is compared with that of an impact printer, one of the problems in the non-impact machine has been the control of the printing operation. As is well-known, the impact operation depends upon the movement of impact members, such as print hammers or wires or the like, which are typically moved by means of an electromechanical system and which may, in certain applications, enable a more precise control of the impact members.
The advent of non-impact printing, as in the case of thermal printing, brought out the fact that the heating cycle must be controlled in a manner to obtain maximum repeated operations. Likewise, the control of ink jet printing, in at least one form thereof, must deal with rapid starting and stopping movement of the ink fluid from a supply of the fluid. In each case of non-impact printing, the precise control of the thermal elements and of the ink droplets is necessary to provide for both correct and high-speed printing.
In the matter of ink jet printing, it is extremely important that the control of the ink droplets be both precise and accurate from the time of formation of the droplets to depositing of such droplets on paper or like record media and to make certain that a clean printed character results from the ink droplets. While the method of printing with ink droplets may be performed in either a continuous manner or in a demand pulse manner, the latter type method and operation is disclosed and is preferred in the present application when applying the features of the present invention. The drive means for the ink droplets is generally in the form of a well-known crystal or piezoelectric type element to provide the high-speed operation for ejecting the ink through the nozzle, while allowing time between droplets for proper operation. The ink nozzle construction must be of a nature to permit fast and clean ejection of ink droplets from the print head.
In the ink jet printer, the print head structure may be a multiple nozzle type with the nozzles aligned in a vertical line and supported on a print head carriage which is caused to be moved or driven in a horizontal direction for printing in line manner, while the ink droplet drive elements or transducers may be positioned in a circular configuration with passageways leading to the nozzles.
Alternatively, the printer structure may include a plurality of equally-spaced, horizontally-aligned, single nozzle print heads which are caused to be moved in back-and-forth manner to print successive lines of dots in making up the lines of characters. In this latter arrangement, the drive elements or transducers are individually supported along a line of printing.
In a still different structure, the nozzles are spaced in both horizontal and vertical directions, and the vertical distance between centers of the ink jets equals the desired vertical distance between one dot and the next adjacent dot above or below the one dot on the paper. The horizontal distance is chosen to be as small as mechanically convenient without causing interference between the actuators, reservoirs, and feed tubes associated with the individual jets. The axes of all jets are aligned approximately parallel to each other and approximately perpendicular to the paper. Thus, if all nozzles were simultaneously actuated, a sloped or slanted row of dots would appear on the paper and show the dots spaced both horizontally and vertically. In order to produce a useful result consisting of dots arranged as characters, it is necessary to sweep the ink jet head array back and forth across the paper, and to actuate each individual nozzle separately when it is properly located to lay down a dot in the desired position. A vertical row of dots is created by sequentially actuating the nozzles rather than simultaneous actuation thereof, the latter being the preferred practice in the more common nozzle arrangements.
In the concept of dot matrix printing, it is generally desired to place the print element actuators in a position to allow characters to be printed in serial manner and this placement requires that the print wires, nozzles, electrodes or other like print actuators be very closely spaced with respect to each other. Since the print actuators are generally larger in size than the diameter of the printed dot, a relatively long wire, channel or like element must be provided to bring the desired print activity from its source, such as a moving armature or plunger or a pressure generating piezoelectric crystal or the like, to a vertical, closely-spaced, column arranged in a pattern such that a column of closely-spaced tangentially coincident or overlapping dots will be produced on the record media if all actuators are fired or actuated at one time. However, it is likely seen that the use of long wires or channels are known to lower the performance of the actuators.
Since it is desirable to eliminate the long curving transition section between the drive elements and the nozzles, as in the case of the circular arrangement mentioned above, it is proposed to provide an array of ink jet transducers in a spaced configuration or manner for use in a compact print head.
Representative documentation in the field of ink jet print heads and in energization thereof includes U.S. Pat. No. 3,397,345, issued to R. J. Dunlavey on Aug. 13, 1968, which discloses an electrode assembly for ink fluid transfer devices wherein a plurality of electrode structures are formed by etching plates of copper-clad glass and making electrical strapping connections between selected electrodes.
U.S. Pat. No. 3,832,579, issued to J. P. Arndt on Aug. 27, 1974, discloses a well-known pulsed droplet ejecting system wherein a liquid carrying conduit includes a portion capable of conducting pressure waves in the liquid by means of an electro-acoustic transducer having leads surrounding the conduit portions and pulsed for causing ejection of droplets from the nozzle.
U.S. Pat. No. 4,180,225, issued to T. Yamada on Dec. 25, 1979, discloses an ink jet recorder which has an inner metal electrode and an outer metal electrode attached to either side of a ceramic wall end of the reservoir around the outlet thereof. A voltage is applied to the electrodes to provide a vibration to the ink stream for ejection of ink from an orifice in the outer electrode.